In the art, it is not easy to obtain a health index of a workpiece processing apparatus. In one aspect, only if the workpiece processing apparatus stops machining in an off-line mode (e.g. when the cutting tool is taken apart and then is subject to precision measurement) may its apparatus health index (e.g. the wear of the cutting tool) be obtained. At an operation mode under which a workpiece is being machined, a health index of the workpiece processing apparatus may not be obtained immediately.
In another aspect, it is not easy to obtain the ground truth related to an apparatus health index, too. A less data quantity of ground truths may cause that a great error occurs to a relevant model for estimating an apparatus health index. For example, an experiment result indicates that a relevant transform model of apparatus health indexes, which is established when the data quantity of ground truths is N/2, may have about 55% more errors than another relevant transform model, which is established when the data quantity of ground truths is N.